This invention relates to a footwear sole assembly. In particular, the invention relates to a flexible footwear sole having a transverse sloped portion.
Footwear is as old as Man. Cave people used it to protect their soles. Progressively, the design of footwear became more specific. For walking comfort, sole designs that mimic the anatomical form of the feet, particularly at the arch, came into being. Other sole designs for various sports and running also came into being, all striving to protect and enhance the natural biomechanical function of ankle-to-foot movement. These designs have one constant: the bottom of the feet lies substantially horizontal, i.e., parallel to ground level.
For the purposes of this disclosure, the upper surface transverse angle, tilt, cant or slope of a portion of a sole of an item of footwear (e.g., a shoe, boot, slipper, etc.) is defined as positive when the top surface of the portion of the sole slopes down outwardly (laterally) and negative when the top surface of the portion of the sole slopes down inwardly (medially). The angle of the slope is expressed as a deviation from the horizontal in degrees. The horizontal is defined as substantially perpendicular to the vertical plane of the wearer of the item of footwear when the wearer is standing still on a horizontal surface and is balanced. This definition is consistent with that used in U.S. Pat. No. 5,036,603, except in this disclosure it applies to portions of the sole.
For the purposes of this disclosure, the lower surface transverse angle, tilt, cant or slope of a portion of a sole of an item of footwear (e.g., a shoe, boot, slipper, etc.) is defined as negative when the lower surface of the portion of the sole slopes down outwardly (laterally) and positive when the lower surface of the portion of sole slopes down inwardly (medially). The angle of the slope is expressed as a deviation from the horizontal in degrees. The horizontal is defined as substantially perpendicular to the vertical plane of the wearer of the item of footwear when the wearer is standing still on a horizontal surface and is balanced.
With advancing age, a person's sense of balance and leg muscle strength deteriorate. Lateral sway in the elderly increases while walking and corrective responses to this imbalance also suffer with age. These factors combine to increase the risk of falling with injurious consequences.
What would help the aged is a footwear structure having means to urge both knees medially towards the wearer's vertical plane that provides optimal balance when standing and walking. The footwear sole of the present invention provides such a structure. A footwear sole having an upper surface that, when loaded, assumes a negative slope in a narrow range of between two and six degrees is sufficient to allow a broad range of people with different anatomical legs forms to benefit from this invention.
The background art is characterized by U.S. Pat. Nos. 4,266,553; 5,036,604; 6,226,901; 6,286,232; 6,360,453; and 6,604,301; the disclosures of which patents are incorporated by reference as if fully set forth herein.
Faiella in U.S. Pat. No. 4,266,553 discloses a sole having a positive transverse slope (see his FIGS. 4, 5 and 6 which his FIG. 2 reveals are cross-sections of a right sole viewed from the back end of the sole). This is contrasted with applicant's invention which envisions a sole surface that assumes a negative transverse slope when loaded.
Rosen in U.S. Pat. No. 5,036,604 discloses an adjustable foot support system. This invention is limited in that the axial rotational transverse canting of the footbed must be adjusted.
Rosen in U.S. Pat. No. 6,226,901 B1 discloses an adjustable foot orthotic. This invention is limited it that adjustment of the transverse angular tilt or cant of the sole is necessary.
Snyder in U.S. Pat. No. 6,286,232 discloses an insole comprising a heel portion having a positive transverse slope. His FIG. 5 shows that his FIG. 9 is a cross-section viewed from the front end of the insole. This teaching is also documented in his specification at col. 6, lines 18-27. This is contrasted with applicant's invention which envisions a sole that assumes a negative transverse slope when loaded.
Ellis, III, in U.S. Pat. No. 6,360,453 discloses corrective shoe sole structures using a contour greater than the theoretically ideal stability plane. This invention is limited in that it teaches that both upper and lower sole surfaces must be substantially horizontal.
Manoli, II et al. in U.S. Pat. No. 6,604,301 disclose a shoe insert support. The Manoli, II et al. reference (U.S. Pat. No. 6,604,301) addresses a disorder termed “cavovarus foot” in which “the foot assumes a posture of an inward tipping of the heel (heel supination or varus, and a related forefoot pronation (forefoot valgus).” The heel portion 12 may have “a lateral heel wedge 13 formed therein to increase the valgus positioning of the heel.” The elevation of the lateral aspect of only the forefoot 26 portion of the insert is an aspect of some embodiments of the Manoli, II et al. invention. This valgus wedge 28 decreases in elevation from the lateral to the medial aspect of the sole insert as shown in their FIGS. 4A and 4C. Their FIG. 3 shows that their FIGS. 4A and 4C are cross-sections of the forefoot portion viewed from the front end of the sole insert. This invention is limited in that providing for lateral flexing of the sole to produce a negative upper surface slope is not taught.
The background art does not teach a flexible sole structure that comprises a heel segment having horizontal upper and lower surfaces combined with other sole segments having arch (instep) and toe upper surfaces that are horizontal when unloaded, but that assume a negative upper surface slope when loaded, and with arch and toe lower surfaces that have a negative lower surface slope with unloaded, but that assume a horizontal position when loaded.